WASHINGTON -- Taking a blood pressure pill at bedtime instead of in the morning might be healthier for some people.

New research suggests that simple switch may normalize patterns of blood pressure in patients at extra risk from the twin epidemics of heart and kidney disease.

Why? When it comes to blood pressure, you want to be a dipper. In healthy people, blood pressure dips at night, by 10 to 20 percent. Scientists don't know why, but suspect the drop gives arteries a little rest.

People with high blood pressure that doesn't dip at night -- the non-dippers -- fare worse than other hypertension sufferers, developing more serious heart disease. Moreover, heart and kidney disease fuel each other -- and the 26 million Americans with chronic kidney disease seem most prone to non-dipping. In addition to heart problems, they're at extra risk of their kidney damage worsening to the point of dialysis.

Most blood pressure patients need two or three medications. So Italian researchers performed an easy test: They told 32 people with kidney disease to switch one of those drugs from a morning to a bedtime dose. In two months, nearly 90 percent of these high-risk patients had turned into dippers. Their nighttime blood pressure dropped an average of 7 points, without side effects or increase in daytime blood pressure.

While the Italian study is too small for proof, similar studies from Europe also back a bedtime switch for non-dippers. The work is catching the attention of U.S. hypertension specialists, and now doctors at Baltimore's Johns Hopkins University are planning a larger study to see if a bedtime switch really could give certain people healthier hearts and kidneys.